"Big Boy" 4014 slowly passes Wahsatch, Utah, heading west on the block of a long stack train ahead. Wahsatch is the top of the grade between Evanston and Ogden, and I understand these engines were designed for the Wahsatch grade and originally were to be known as the Wahsatch (or Wasatch) class, but then somebody at Alco chalked the Big Boy on the smoke box and it caught on.